1. Field of the Invention
The present invention relates generally to a method and an apparatus for treating apnea and, more particularly, to a method and an apparatus for diagnosing and treating sleep apnea in a single night.
The term “apnea”, as used herein, is meant to encompass any type of breathing disorder, for example, apnea (complete cessation of breathing), patency obstruction, partial obstruction, apnea that arises in patients with various cardiac, cerebrovascular and endocrine conditions unrelated to the state of the upper airway, or the like.
2. Description of the Background Art
Sleep apnea arises during sleep when a patient undergoes repeated cessation of breathing. The cessation is caused by an obstruction of the throat air passage. Repeated cessation of breathing reduces blood oxygen and disturbs sleep. Reduction of blood oxygen can cause heart attacks and strokes, while sleep disturbances or fragmentation can produce excessive daytime sleepiness.
Treatment of sleep apnea typically occurs in two stages: assessment (diagnosis) and titration. In the first stage, the patient is monitored for signs of disordered breathing. In the second stage, the patient wears a continuous positive airway pressure (CPAP) mask. The CPAP mask covers the nose of the patient and forms a pressure seal with the surrounding face. While the patient sleeps, air pressure in the mask is slowly increased until signs of apnea cease.
In the past, the two stages occurred in a specialized hospital sleep center on two consecutive nights. More recently, both stages occur in a single night, the so-called “split night” method. In such cases, however, both stages are performed in a hospital sleep center.
Recent clinical results have shown the value of conducting diagnostic testing (assessment) in the home, and portable diagnostic devices are now available for this purpose. Advantages include lower cost, increased comfort of the patient, and a more realistic assessment of sleep patterns under normal home conditions. However, the patient still needs to return to a hospital sleep center for titration.
An “auto-CPAP” device is capable of performing titration on a patient who has already been diagnosed. Such devices monitor a limited range of physiologic variables and attempt to set the pressure in the CPAP mask to an optimal value. In other words, the minimum level of pressure (i.e., titration pressure) required to produce a patent pharyngeal airway or the necessary therapeutic pressure required for properly treating the patient is determined. Some clinicians have sought to use the auto-CPAP device as a substitute for conventional sleep studies. However, the severity of the illness in the absence of CPAP pressure is never determined. Even if the auto-CPAP device can accurately determine the titration pressure, no baseline exists for comparing to standard diagnostic criteria.
While the aforementioned auto-CPAP device is an improvement over the conventional CPAP device, there continue to be a need in the art for an improved diagnostic method and system for diagnosing and treating sleep apnea in a single night, preferably in the home.